Negative pressure gauge zero-check
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1. Range: -4 to 4 KPa. If zero calibration shows 0 KPa at 4 mA, it indicates that the gauge is accurate. If it shows 0.5 when zeroing out, my measurement range is set to -4.5–3.5. Another idea: I could first change the range to 0–8, perform zeroing with 475, and then change the range to -4–4. Which of these methods is correct? Or are neither correct? Please help explain!
I’m confused too. The range is -4 kPa to 4 kPa; when zeroing it and checking at 4 mA, it shows 0 kPa. Does this mean the gauge is accurate?
First, change the range to 0–8; after zeroing at 4,750, change the range to -4–4. That’s correct
1. Range: -4 to 4 KPa. If the zero-check shows 0 KPa at 4 mA, it means the gauge is accurate. Brother, if it’s really accurate, then all the gauges in your factory would likely need to be replaced
The value for the atmosphere is 0; shouldn’t it be 12mA?
None of them are correct; it’s complete chaos.
-4~4 ma: 0% = -4 kPa, 25% = -2 kPa, 50% = 0 kPa, 75% = 2 kPa, 100% = 4 kPa.
The calibration of a negative pressure gauge is the same as that of a positive pressure gauge: 4 mA corresponds to the lower limit of the range, while 20 mA corresponds to the upper limit of the range. HART can be used to change the range of the instrument as well as its zero point; generally, it refers to a zero point at zero, not a negative value – this concept must be clearly understood
4ma must be the lower limit of your range, not “0”; the original poster is a bit confused about this concept! First, change the range to 0–8; after zeroing at 4,750, change the range to -4–4. That’s correct
Thank you for the correction. One more question: when it is reset to zero, the pressure is 0 KPA, but the displayed value is not 12 mA. Is this due to some kind of drift or what else?
After changing it to 0---8, 475 resets to zero; then by setting the range to -4---4, it shouldn’t affect the sensitivity of the gauge, right?